The invention concerns a device for use in filtering separators with, in particular, bag, pouch-, or cartridge-shaped filtering means.
In order to measure the air permeability of soiled filter bags, the relevant filter bag must be removed, packaged, and shipped to the laboratory which performs such measurements. In the often long period between removal and laboratory examination, the filter bag and the dust adhering to it are subject to considerable changes. This is due on the one hand to environmental influences, in particular the action of atmospheric humidity. On the other hand, the dust cake is destroyed as the filter bag is flexed and rolled up during and after removal. For these reasons, the air permeability values measured in the laboratory can be only imprecisely evaluated, and even then only with reference to previous examinations. The performance of the system can be indicated only vaguely, and in consideration of values gained by experience.
Heavily soiled or encrusted filter bags can at present be cleaned only by being subjected to dry or wet cleaning outside the filtration system, i.e. after they are removed. The same expenditure of time and money is therefore involved as for a complete change of the filter bag. In the case of a wet wash, the filter bag must be transported, wet-washed, and dried. Suitable working spaces are required for this, along with the use of personal safety clothing so as to protect persons working with it from the filter dust, which in some case is also contaminated. In addition, the surface finish effected by calendering or singeing is largely lost. Surface coatings can also be irreversibly damaged. The filter bags moreover tend to shrink and become felted when wet-washed.
It is known to dedust filter bags in a filtration system by means of a permanently installed pulse-jet system, by generating compressed air pulses simultaneously, via small nozzles, in all the filter bags. This type of dedusting is of only limited effectiveness, however, and therefore also cannot replace dry or wet cleaning outside the filtration system.